In this scenario, most of the AGNs observed in
the local Universe are not associated with star bursts,
although their host galaxies may have gone
through star burst phases earlier. Indeed, the
analyses on the H\(\delta \)  absorption line
have revealed that a significant fraction of AGNs
reside in post-star-burst galaxies [1]}.
The early star burst in the center of a galaxy can
help to build up a central bulge.
This may explain why galaxies of larger
\(\sigma _*\)  on average are surrounded by
larger number of satellites (Figure REF ).
The connection between star burst and AGN activity is also
supported by the high AGN fraction in galaxies with \(D_n4000\sim 1\) 
(Figure REF ). Since AGNs in star burst galaxies (\(D_n4000<1.2\) )
are directly triggered by galaxy interaction, while AGNs hosted by
galaxies in the transition from star-forming to quiescent populations
(\(D_n4000\sim 1.5\) ) are mainly driven by secular evolution,
two characteristic time scales are relevant here: the star
burst time scale, which is typically \(10^8\)  years, and the secular
evolution time scale, which is typically a few Gyrs for present-day
galaxies. The two peak distribution shown in Figure REF 
may be explained by these two time scales.
